12leadsecg01

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ECGdiagnosis

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ims

10 ECG rules

ECG signs of M.I.

Evolution of changes in M.I.Classical Appearences

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QRS waveform nomenclature

R r qR qRs Qrs QS

Qr Rs rS qs rSr rSR

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The 10 rules for a normal ECG

I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

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Rule 1

PRinterval

Millivo

lts

Milliseconds

0 200 400 600

-0.5

0

0.5

1.0

P

R

TQ

S

PR interval should be 120 to

200 milliseconds or 3 to 5 littlesquares

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Rule 2

Millivo

lts

Milliseconds

0 200 400 600

-0.5

0

0.5

1.0

QRS

P

R

TQ

S

The width of the QRS complex

should not exceed 110 ms, lessthan 3 little squares

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Rule 3

I II III aVR aVL aVF

The QRS complex should be

dominantly upright in leads I and II

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Rule 4

I II III aVR aVL aVF

QRS and T waves tend to have the

same general direction in the limbleads

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Rule 5

P

Q

T

S

All waves are negative in lead aVR

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Rule 6

V1V2

V3V4

V5V6

The R wave in the precordial leads must grow from V1 to at least V

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Rule 7

The ST segment should start isoelectric except in V1 and

V2 where it may be elevated

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Rule 8


The P waves should be upright in I, II, and V2 to V6

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Rule 9


There should be no Q wave or only a small q less than

0.04 seconds in width in I, II, V2 to V6

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Rule 10


The T wave must be upright in I, II, V2 to V6

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Characteristic changes in AMI

ST segment elevation over area of damage

ST depression in leads opposite infarction

Pathological Q waves

Reduced R waves Inverted T waves

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ST elevation

R

P

Q

ST

Occurs in the early

stages

Occurs in the leads

facing the infarction

Slight ST elevation may

be normal in V1or V2

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Deep Q wave

R

P

Q

T

ST

Only diagnostic change of

myocardial infarction

At least 0.04 seconds in duration

Depth of more than 25% of

ensuing R wave

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T wave changes

R

P

Q

T

ST

Late change

Occurs as ST elevation is

returning to normal

Apparent in many leads

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Bundle branch block

I II III aVR aVL aVF V1 V2 V3 V4 V5 V6 I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

Anterior wall MILeft bundle branch block

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Sequence of changes in evolving AMI

1 minute after onset 1 hour or so after onset A few hours after onset

A day or so after onset Later changes A few months after AMI

Q

RP

Q T

STR

P

Q

ST

P

QT

ST

R

PS

T

P

QT

ST

RP

Q

T

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Anterior infarction

Anterior infarction


Left

coronary

artery

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Inferior infarction

Inferior infarction


Right

coronary

artery

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Lateral infarction

Lateral infarction


Left

circumflex

coronary

artery

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Location of infarct combinations

aVR V1 V4I

II

III

LATERAL

INFERIOR

ANTPOST ANT

SEPTAL

ANT

LAT

aVL

aVF

V2

V3

V5

V6

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Diagnostic criteria for AMI

Q wave duration of more than 0.04

seconds

Q wave depth of more than 25% of

ensuing r wave

ST elevation in leads facing infarct (ordepression in opposite leads)

Deep T wave inversion overlying and

adjacent to infarct

Cardiac arrhythmias

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